Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$170.33	5.128%	$179.0645	$179.06	$179.05	$179.10
Purchase #2	$155.58	8.713%	$169.1357	$169.14	$169.15	$169.10
Purchase #3	$174.75	8.451%	$189.5181	$189.52	$189.50	$189.50
Purchase #4	$63.60	13.745%	$72.3418	$72.34	$72.35	$72.30
Purchase #5	$224.52	13.438%	$254.691	$254.69	$254.70	$254.70
Purchase #6	$242.57	3.179%	$250.2813	$250.28	$250.30	$250.30
Purchase #7	$28.37	12.681%	$31.9676	$31.97	$31.95	$32.00
7 purchase totals =	$1,059.72		$1,147.0000	$1,147.00	$1,147.00	$1,147.00